Duncan, 54, died at Cedars-Sinai Medical Center in Los Angeles, according to a statement from his publicist, Joy Fehily. He had suffered a heart attack in July and did not recover.

Craig Harvey of the coroner's office said Tuesday that there was nothing to suggest officials needed to review the case. Officials noted Duncan had heart problems and was under medical care.

In such cases, it is normal for the doctor to sign the death certificate without any review by the coroner.

A former ditch digger for a natural gas company in his native Chicago, Duncan began his Hollywood saga as a celebrity bodyguard in the mid-1990s, according to his Times obituary. He received his first big acting break playing a member of the team sent into space to blow up an asteroid heading to Earth in the big-budget 1998 movie "Armageddon," starring Bruce Willis.

But it was "The Green Mile," starring Tom Hanks as a death-row prison guard in a Louisiana penitentiary during the Depression, that thrust the 6-foot-5, 300-plus-pound Duncan into the limelight. He portrayed John Coffey, a gentle giant with supernatural powers who was sentenced to death for the murder of two young white girls.

"There was something about him that I just couldn't ignore," writer-director Frank Darabont said of Duncan in a 2000 Daily Variety interview. "After his first reading, he kept haunting me. Given that he was a fairly inexperienced actor at that point, obviously there was a concern about 'Gee, how would this guy do?'

"But once we put him on film, it became apparent that he was up to the task."

Duncan was born Dec. 10, 1957, and grew up on Chicago's South Side. His father left the family when he was 6, and he and his sister were raised by their mother, who steered him clear of gangs, drugs and alcohol.

Growing up, he harbored dreams of becoming an actor.

"Of course, people told me, 'Mikey, you will never be an actor. You don't have the look. You're ugly,'" he recalled in a 2003 Chicago Sun-Times interview.

Besides his mother, Jean, and his sister, Judith, he is survived by his fiancee, actress Omarosa Manigault.